We don't even have 2WD's accurate, the content currently is the main problem. Racer itself is very good physics-wise. We don't have accurate pacejka for a start, its all mostly guessed values, and if the tyres aren't right, it's never going to be right no matter how accurate everything else is.
It will improve, when 090's out a lot more content will appear, and it'll get more realistic with time. 4WD will also come, along with other features. Patience is a virtue, and a necessity with Racer.